Safety glass is used in many glass applications for which improved impact resistance and glass retention is desirable. A prominent example of safety glass use is as a windshield for motor vehicle applications.
Safety glass is available in many configurations. Commonly, safety glass is composed of a polymeric interlayer disposed between two layers of glass. The polymeric interlayer can be, for example, a single sheet or multiple sheets. The polymeric material is typically a plasticized poly(vinyl butyral) that functions in an accident to both absorb energy and retain fragmented glass.
Safety glass is typically made by initially assembling a sheet of polymeric interlayer between two panes of glass. The assembly is then fed to a de-air oven where heat and force are applied to tack, or partially bond, the interlayer to the glass. The prelaminate thus formed is then placed in an autoclave, where temperature and pressure are applied in order to finish the bonding process and create an optically clear, impact resistant safety glazing.
While well known and straightforward, this conventional lamination technique is replete with procedural difficulties that are labor intensive, time consuming, and pose safety concerns. For example, during the initial assembly of the components, the interlayer sheet is typically larger than the bounding glass and is usually trimmed flush with the edges of the glass. This operation typically requires manual labor, often limits throughput, and poses a safety concern.
Further, the conventional lamination process is energy intensive and time-consuming, both of which increase the cost and production time for laminated glass. For example, the three main steps—assembly, de-air, and autoclave—each require significant amounts of time, resulting in a total fabrication process that can easily add up to 8 hours from start to finish. Furthermore, much of the energy supplied to one process, such as the thermal energy supplied to the de-air process, is typically not carried over to the following autoclave step, which requires additional thermal energy.
One proposed solution to the limitations inherent in conventional lamination techniques is disclosed in European Patent Application 0908287 (Komatsu)(see also U.S. Pat. Nos. 6,296,799, 6,669,890, and 6,368,537) which discloses the injection of resin into a glass insert, followed by compression of the mold cavity.
What are needed in the art are methods of producing glass panels, and other glazing panels, that do not require extensive fabrication procedures and that allow for the rapid and inexpensive formation of multiple layer glazings.